The effects of urban green space and road proximity to indoor traffic-related PM2.5, NO2, and BC exposure in inner-city schools

BACKGROUND

Since there are known adverse health impacts of traffic-related air pollution, while at the same time there are potential health benefits from greenness, it is important to examine more closely the impacts of these factors on indoor air quality in urban schools.

OBJECTIVE

This study investigates the association of road proximity and urban greenness to indoor traffic-related fine particulate matter (PM2.5), nitrogen dioxide (NO2), and black carbon (BC) in inner-city schools.

METHODS

PM2.5, NO2, and BC were measured indoors at 74 schools and outdoors at a central urban over a 10-year period. Seasonal urban greenness was estimated using the Normalized Difference Vegetation Index (NDVI) with 270 and 1230 m buffers. The associations between indoor traffic-related air pollution and road proximity and greenness were investigated with mixed-effects models.

RESULTS

The analysis showed linear decays of indoor traffic-related PM2.5, NO2, and BC by 60%, 35%, and 22%, respectively for schools located at a greater distance from major roads. The results further showed that surrounding school greenness at 270 m buffer was significantly associated (p < 0.05) with lower indoor traffic-related PM2.5: -0.068 (95% CI: -0.124, -0.013), NO2: -0.139 (95% CI: -0.185, -0.092), and BC: -0.060 (95% CI: -0.115, -0.005). These associations were stronger for surrounding greenness at a greater distance from the schools (buffer 1230 m) PM2.5: -0.101 (95% CI: -0.156, -0.046) NO2: -0.122 (95% CI: -0.169, -0.075) BC: -0.080 (95% CI: -0.136, -0.026). These inverse associations were stronger after fully adjusting for regional pollution and meteorological conditions.

IMPACT STATEMENT

More than 90% of children under the age of 15 worldwide are exposed to elevated air pollution levels exceeding the WHO's guidelines. The study investigates the impact that urban infrastructure and greenness, in particular green areas and road proximity, have on indoor exposures to traffic-related PM2.5, NO2, and BC in inner-city schools. By examining a 10-year period the study provides insights for air quality management, into how road proximity and greenness at different buffers from the school locations can affect indoor exposure.

Plasma metabolite profiles in children with current asthma

BACKGROUND

Identifying metabolomic profiles of children with asthma has the potential to increase understanding of asthma pathophysiology.

OBJECTIVE

To identify differences in plasma metabolites between children with and without current asthma at mid-childhood.

METHODS

We used untargeted mass spectrometry to measure plasma metabolites in 237 children (46 current asthma cases and 191 controls) in Project Viva, a birth cohort from eastern Massachusetts, USA. Current asthma was assessed at mid-childhood (mean age 8.0 years). The ability of a broad spectrum metabolic profile to distinguish between cases and controls was assessed using partial least squares discriminant analysis. We used logistic regression models to identify individual metabolites that were differentially abundant by case-control status. We tested significant metabolites for replication in 411 children from the VDAART clinical trial.

RESULTS

There was no evidence of a systematic difference in the metabolome of children reporting current asthma vs. healthy controls according to partial least squares discriminant analysis. However, several metabolites were associated with odds of current asthma at a nominally significant threshold (P < .05), including a metabolite of nicotinamide (N1-Methyl-2-pyridone-5-carboxamide (Odds Ratio (OR) = 2.8 (95% CI 1.1-8.0)), a pyrimidine metabolite (5,6-dihydrothymine (OR = 0.4 (95% CI 0.2-0.9)), bile constituents (biliverdin (OR = 0.4 (95%CI 0.1-0.9), taurocholate (OR = 2.0 (95% CI 1.2-3.4)), two peptides likely derived from fibrinopeptide A (ORs from 1.6 to 1.7), and a gut microbiome metabolite (p-cresol sulphate OR = 0.5 (95% CI 0.2-0.9)). The associations for N1-Methyl-2-pyridone-5-carboxamide and p-cresol sulphate replicated in the independent VDAART population (one-sided P values = .03-.04).

CONCLUSIONS AND CLINICAL RELEVANCE

Current asthma is nominally associated with altered levels of several metabolites, including metabolites in the nicotinamide pathway, and a bacterial metabolite derived from the gut microbiome.

Asthma and allergy development: contrasting influences of yeasts and other fungal exposures

BACKGROUND

Infancy is a developmental stage with heightened susceptibility to environmental influences on the risk of chronic childhood disease. Few birth cohort studies have detailed measures of fungal diversity data in infants' bedrooms, limiting the potential to measure long-term associations of these complex exposures with development of asthma or allergy.

OBJECTIVE

We evaluated the relation of home fungal levels in infancy to repeated measures of wheeze and development of asthma and rhinitis by age 13, and sensitization by age 12 years.

METHODS

In the Epidemiology of Home Allergens and Asthma prospective birth cohort study, we recruited 408 children with family history of allergic disease or asthma. When children were aged 2-3 months, we measured culturable fungi in bedroom air and dust, and in outdoor air. Main outcomes included ascertainment of symptoms/disease onset by questionnaire from birth through age 13. We estimated hazard ratios and, for wheeze and sensitization, odds ratios for an interquartile increase in log-transformed fungal concentrations, adjusting for other outcome predictors and potential confounders.

RESULTS

Elevated levels of yeasts in bedroom floor dust were associated with reduced: i) wheeze at any age; ii) fungal sensitization; and iii) asthma development by age 13 (hazard ratio (HR) = 0.86; 95% confidence interval (CI), [0.75 to 0.98]). Outdoor airborne Cladosporium and dustborne Aspergillus predicted increased rhinitis. Risk of fungal sensitization by age 12, in response to environmental Alternaria and Aspergillus, was elevated in children with a maternal history of fungal sensitization.

CONCLUSIONS AND CLINICAL RELEVANCE

Despite the irritant and allergenic properties of fungi, early-life elevated dust yeast exposures or their components may be protective against allergy and asthma in children at risk for these outcomes. Ascertainment of fungal components associated with immunoprotective effects may have therapeutic relevance for asthma.

Developmental determinants in non-communicable chronic diseases and ageing

Prenatal and peri-natal events play a fundamental role in health, development of diseases and ageing (Developmental Origins of Health and Disease (DOHaD)). Research on the determinants of active and healthy ageing is a priority to: (i) inform strategies for reducing societal and individual costs of an ageing population and (ii) develop effective novel prevention strategies. It is important to compare the trajectories of respiratory diseases with those of other chronic diseases.

Allergens on desktop surfaces in preschools and elementary schools of urban children with asthma

Desktop dust has been studied as a source of food allergen, but not as a source of potential aeroallergen exposure. Thirty-six wiped samples from desktop surfaces were collected from preschools and schools. Samples were analyzed for detectable levels of common aeroallergens including Alternaria, cockroach, dog, dust mite, cat, mouse, and rat allergens by immunoassay. Mouse allergen was the most prevalent, detectable in 97.2% of samples. Cat allergen was detectable in 80.6% of samples, and dog allergen was detectable in 77.8% of samples. Other allergens were not as prevalent. Mouse was the only allergen that was highly correlated with settled floor dust collected from the same rooms (r = 0.721, P < 0.001). This is the first study to detect aeroallergens on desktop surfaces by using moist wipes. Allergens for mouse, cat, and dog were highly detectable in wipes with mouse desktop surface levels correlating with levels in vacuumed floor dust.

Wheeze in infancy: protection associated with yeasts in house dust contrasts with increased risk associated with yeasts in indoor air and other fungal taxa

BACKGROUND

While fungal exposures are assumed to provoke wheeze through irritant or allergenic mechanisms, little is known about the differential effects of indoor and outdoor fungi on early-life wheeze.

METHODS

In a Boston prospective birth cohort of 499 at-risk infants, culturable fungi in bedroom air and dust and outdoor air were measured at the age of 2-3 months. Wheeze was determined using bimonthly telephone questionnaires. Odds ratios were estimated for an interquartile increase in fungal natural log-transformed concentrations, adjusting for predictors of wheeze and potential confounders.

RESULTS

Increased odds of 'any wheeze' (≥1 vs 0 episodes) by age one were positively associated with indoor dust Alternaria [odds ratio (OR) = 1.83; 95% confidence interval (CI), 1.07-3.14], Penicillium [OR = 1.18; (0.98-1.43)], and Cladosporium [OR = 1.47; (1.16-1.85)]; indoor air Penicillium [OR = 1.26; (0.92-1.74)]; and outdoor air Cladosporium [OR = 1.68; (1.04-2.72)]. In contrast, indoor dust yeasts were protective [OR = 0.78; (0.66-0.93)]. 'Frequent wheeze' (≥2 vs <2 episodes) by age one was borderline associated with dust yeasts [OR = 0.86; (0.70-1.04)] and indoor air yeasts [OR = 1.53; (0.93-2.53)]. Alternaria concentration was associated with any wheeze for children with maternal mold sensitization [OR = 9.16; (1.37-61.22)], but not for those without maternal mold sensitization [OR = 1.32; (0.79-2.20)].

CONCLUSIONS

While wheeze rates were higher with exposures to fungal taxa considered to be irritant or allergenic in sensitive subjects, yeasts in the home had a strong protective association with wheeze in infancy. Molecular microbiologic studies may elucidate specific components of innate microbiologic stimulants that lead to contrasting effects on wheeze development.

Maternal intestinal flora and wheeze in early childhood

BACKGROUND

Increasing evidence links altered intestinal flora in infancy to eczema and asthma. No studies have investigated the influence of maternal intestinal flora on wheezing and eczema in early childhood.

OBJECTIVE

To investigate the link between maternal intestinal flora during pregnancy and development of wheeze and eczema in infancy.

METHODS

A total of 60 pregnant women from the Boston area gave stool samples during the third trimester of their pregnancy and answered questions during pregnancy about their own health, and about their children's health when the child was 2 and 6 months of age. Quantitative culture was performed on stool samples and measured in log(10)colony-forming units (CFU)/gram stool. Primary outcomes included infant wheeze and eczema in the first 6 months of life. Atopic wheeze, defined as wheeze and eczema, was analysed as a secondary outcome.

RESULTS

In multivariate models adjusted for breastfeeding, day care attendance and maternal atopy, higher counts of maternal total aerobes (TA) and enterococci (E) were associated with increased risk of infant wheeze (TA: OR 2.32 for 1 log increase in CFU/g stool [95% CI 1.22, 4.42]; E: OR 1.57 [95% CI 1.06, 2.31]). No organisms were associated with either eczema or atopic wheeze.

CONCLUSIONS AND CLINICAL RELEVANCE

In our cohort, higher maternal total aerobes and enterococci were related to increased risk of infant wheeze. Maternal intestinal flora may be an important environmental exposure in early immune system development.

Longitudinal relationship of early life immunomodulatory T cell phenotype and function to development of allergic sensitization in an urban cohort

BACKGROUND

Immunomodulatory T cells are thought to influence development of allergy and asthma, but early life longitudinal data on their phenotype and function are lacking.

OBJECTIVES

As part of the Urban Environment and Childhood Asthma (URECA) study, we investigated the development of immunomodulatory T cell phenotype and function, and characterized their relation to allergic disease progression from birth through to 2 years of age.

METHODS

Immunomodulatory T cell phenotype and function in cord blood mononuclear cells (CBMC) and peripheral blood mononuclear cells (PBMC) at 1 and 2 years of age were characterized by analysing CD25(bright) and FoxP3(+) expression, proliferative responses and cytokine production. The relation of immunomodulatory T cell characteristics to allergic sensitization and disease at 1- and 2-years of age was investigated.

RESULTS

The proportion of CD4(+)CD25(bright) and CD4(+)CD25(+)FoxP3(+)T cells (n = 114, 83, 82 at birth, 1- and 2-years respectively) increased significantly, whereas there were no significant changes in the suppressive function of CD25(+)T cells (n = 78, 71, 81 at birth, 1- and 2-years respectively). Birth immunomodulatory T cell characteristics were not related to subsequent allergic sensitization or disease. However, increases in the numbers of CD4(+)CD25(bright) cells and their ability to suppress lymphoproliferative responses at 1 year of age were associated with reduced allergic sensitization at 1 (P = 0.03) and 2 (P = 0.02) years of age. Production of the anti-inflammatory cytokine IL-10 by CD25(+)T cells appeared to mediate this protective suppressive function. In contrast, by 2 years of age, we observed the emergence of a positive association of CD4(+)CD25(+) FoxP3(+) T cell numbers with allergic sensitization (P = 0.05) and eczema (P = 0.02).

CONCLUSIONS AND CLINICAL RELEVANCE

These findings suggest that the relationship between immunomodulatory T cell subsets, allergic sensitization and eczema is developmentally regulated. In the first year of life, CD4(+)CD25(+) IL-10 producing T cells are associated with a reduced incidence of allergic sensitization. Once allergic sensitization or eczema is established, CD4(+)CD25(+)FoxP3(+)T-reg cells expand to potentially counteract the allergic inflammatory response. Understanding the relationship between development of immunoregulatory T cells and early onset atopy could lead to new preventive strategies for allergic diseases.

Umbilical cord plasma 25-hydroxyvitamin D concentration and immune function at birth: the Urban Environment and Childhood Asthma study

BACKGROUND

Recent studies have reported conflicting data on the association between maternal intake of vitamin D during pregnancy and asthma.

OBJECTIVE

To assess the influence of prenatal vitamin D status on immune function at birth.

METHODS

In an inner-city birth cohort of 568 newborns, 520 of whom had at least one atopic parent, we measured the umbilical cord (UC) plasma concentration of 25-hydroxyvitamin D (25(OH)D) and the cytokine responses of UC blood mononuclear cells (UCMCs) to stimuli including phytohaemagglutinin (PHA), lipopolysaccharide (LPS), and peptidoglycan. In a subset, the UCMC expression of regulatory T cell markers and the suppressive activity of CD4(+) CD25(+) UCMCs were measured. Results The 25th, 50th, and 75th percentiles of UC plasma 25(OH)D level were 15.0, 20.2, and 25.6 ng/mL, respectively. Most cytokine responses of UCMC were not correlated with UC 25(OH)D concentration; however, IFN-γ release after LPS stimulation was weakly positively correlated with UC 25(OH)D concentration (r=0.11, P=0.01). PHA responses were not significantly correlated with 25(OH)D concentration. The UC plasma 25(OH)D concentration was inversely related to the number of CD25(+) (r=-0.20, P=0.06), CD25(Bright) (r=-0.21, P=0.05), and CD25(+) FoxP3 (r=-0.29, P=0.06) cells as a proportion of CD4(+) T cells in UC blood (r=-0.26, P=0.04) but not to the suppressive activity of CD4(+) CD25(+) cells (r=0.17, P=0.22).

CONCLUSION AND CLINICAL RELEVANCE

UC 25(OH)D concentration was not correlated with most UCMC cytokine responses to multiple stimuli. There was a suggestion of a weakly positive correlation with IFN-γ release after LPS stimulation. The proportions of CD25(+) , CD25(Bright) , and CD25(+) FoxP3 cells to total CD4(+) T cells were inversely correlated with UC 25(OH)D concentration. Our findings suggest that higher vitamin D levels at birth may be associated with a lower number of T-regulatory cells. Vitamin D status in utero may influence immune regulation in early life.

Multiple microbial exposures in the home may protect against asthma or allergy in childhood

BACKGROUND

Experimental animal data on the gram-negative bacterial (GNB) biomarker endotoxin suggest that persistence, dose, and timing of exposure are likely to influence its effects on allergy and wheeze. In epidemiologic studies, endotoxin may be a sentinel marker for a microbial milieu, including gram-positive bacteria (GPB) as well as GNB, that may influence allergy and asthma through components (pathogen-associated molecular patterns) that signal through innate Toll-like receptor pathways.

OBJECTIVE

To determine the influence of current GNB and GPB exposures on asthma and allergic sensitization in school-aged children.

METHODS

We examined the relationship between bacterial biomarkers and current asthma and allergic sensitization in 377 school-aged children in a birth cohort study. We then evaluated the effects of school-aged endotoxin, after controlling for exposure in early life.

RESULTS

Exposure to GNB was inversely associated with asthma and allergic sensitization at school age [for >median endotoxin: prevalence odds ratio (POR)=0.34, 95% CI=0.2-0.7, for current asthma and prevalence ratio=0.77, 95% CI=0.6-0.97, for allergic sensitization]. In contrast, elevated GPB in the bed was inversely associated with current asthma (POR=0.41, 95% CI=0.2-0.9) but not with allergic sensitization (POR=1.07, 95% CI=0.8-1.4). School-aged endotoxin exposure remained protective in models for allergic disease adjusted for early-life endotoxin.

CONCLUSION

Both GNB and GPB exposures are associated with decreased asthma symptoms, but may act through different mechanisms to confer protection. Endotoxin exposure in later childhood is not simply a surrogate of early-life exposure; it has independent protective effects on allergic disease.

Mouse allergen exposure, wheeze and atopy in the first seven years of life

BACKGROUND

Little is known about mouse allergen exposure in home environments and the development of wheezing, asthma and atopy in childhood.

OBJECTIVE

To examine the relation between mouse allergen exposure and wheezing, atopy, and asthma in the first 7 years of life.

METHODS

Prospective study of 498 children with parental history of allergy or asthma followed from birth to age 7 years, with longitudinal questionnaire ascertainment of reported mouse exposure and dust sample mouse urinary protein allergen levels measured at age 2-3 months.

RESULTS

Parental report of mouse exposure in the first year of life was associated with increased risk of transient wheeze and wheezing in early life. Current report of mouse exposure was also significantly associated with current wheeze throughout the first 7 years of life in the longitudinal analysis (P = 0.03 for overall relation of current mouse to current wheeze). However, early life mouse exposure did not predict asthma, eczema or allergic rhinitis at age 7 years. Exposure to detectable levels of mouse urinary protein in house dust samples collected at age 2-3 months was associated with a twofold increase in the odds of atopy (sensitization to >=1 allergen) at school age (95% confidence interval for odds ratio = 1.1-3.7; P = 0.03 in a multivariate analysis.

CONCLUSIONS

Among children with parental history of asthma or allergies, current mouse exposure is associated with increased risk of wheeze during the first 7 years of life. Early mouse exposure was associated with early wheeze and atopy later in life.

Fetal cord blood: aspects of heightened immune responses

Neonatal immune responses have been associated with the development of atopy in childhood. We assessed in cord blood mononuclear cells (CBMC) whether increased allergen/mitogen-induced lymphoproliferation (LP) is associated with pro-allergic Th2 cytokine IL-13 or Th1 cytokine IFN-gamma secretion. We determined whether LP to one allergen is related to heightened lymphocyte function to other allergens/mitogen. CBMC from 135 neonates were stimulated with house dust mite (Derf1), cockroach, ovalbumin, or mitogen. LP to one allergen was associated with significantly increased LP to other allergens/mitogen. Increased Derf1-LP was associated with increased Derf1-induced IL-13 secretion (r = 0.21, p = 0.01). After adjusting for neonatal gender, race, and maternal smoking, Derf1-LP remained associated with Derf1-IL-13 (OR 3.08, 95% CI 1.56-6.10). Increased mitogen-induced proliferation was associated with increased mitogen-induced IL-13 secretion (r = 0.37, p < 0.001). For some individuals, a predisposition to a heightened immune response is already evident at birth. Whether this phenotype results in atopy in childhood warrants further investigation.

Elevated allergen-induced IL-13 secretion predicts IgE elevation in children ages 2-5 years

It is unclear if early immune responses to allergens, specifically Th1 and Th2 cytokine production, predict later immune responses, including increased IgE levels. In a group of children (n = 151) with a parental history of allergy or asthma followed from ages 2 through 5 years, we examined IL-13, IL-4, and IFN-gamma secretion by peripheral blood mononuclear cells in response to phytohemagglutinin (PHA), and to dust mite (Der f 1), cockroach (Bla g 2), and cat (Fel d 1) allergens in relation to elevated IgE. Elevated IgE was defined either as a positive IgE-specific response to at least one allergen (dust mite, cockroach, cat, and ovalbumin) or as an elevated total IgE level above a specified cut-off value. In multivariate logistic regression models including 181 observations made between the age of 2 through 5 years and accounting for repeated measures, we found an association between increased IL-13 secretion in response to Der f 1 and elevated IgE (odds ratio [OR] = 1.21, 95% confidence interval [CI] = 1.09-1.34). Age did not modify this relationship. No association was found between allergen-induced IFN-gamma secretion and IgE production. Among the group of children with measurements made at age 4-5 (n = 70), IL-13 in response to Der f 1 (p = 0.046), and IL-4 in response to PHA (p = 0.04) were increased among children with elevated IgE. In a smaller subset of children with measurements made at both age 2-3 and age 4-5 (n = 36), IL-13 levels at age 2-3 were also significantly increased in response to Der f 1 (p = 0.01) and Fel d 1 (p = 0.002) among those with elevated IgE at age 4-5. In a group of children ages 2-5 years, there is an association between IL-13 and elevated IgE.

Air pollution and inflammation in type 2 diabetes: a mechanism for susceptibility

BACKGROUND

Particulate air pollution has been associated with several adverse cardiovascular health outcomes, and people with diabetes may be especially vulnerable. One potential pathway is inflammation and endothelial dysfunction-processes in which cell adhesion molecules and inflammatory markers play important roles.

AIM

To examine whether plasma levels of soluble intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and von Willebrand factor (vWF) were associated with particle exposure in 92 Boston area residents with type 2 diabetes.

METHODS

Daily average ambient levels of air pollution (fine particles (PM2.5), black carbon (BC) and sulphates) were measured approximately 500 m from the patient examination site and evaluated for associations with ICAM-1, VCAM-1 and vWF. Linear regressions were fit to plasma levels of ICAM-1, VCAM-1 and vWF, with the particulate pollutant index, apparent temperature, season, age, race, sex, glycosylated haemoglobin, cholesterol, smoking history and body mass index as predictors.

RESULTS

Air pollutant exposure measures showed consistently positive point estimates of association with the inflammatory markers. Among participants not taking statins and those with a history of smoking, associations between PM(2.5), BC and VCAM-1 were particularly strong.

CONCLUSIONS

These results corroborate evidence suggesting that inflammatory mechanisms may explain the increased risk of air pollution-associated cardiovascular events among those with diabetes.

Ambient particulate air pollution and cardiac arrhythmia in a panel of older adults in Steubenville, Ohio

OBJECTIVES

Ambient particulate air pollution has been associated with increased risk of cardiovascular morbidity and mortality. Pathways by which particles may act involve autonomic nervous system dysfunction or inflammation, which can affect cardiac rate and rhythm. The importance of these pathways may vary by particle component or source. In an eastern US location with significant regional pollution, the authors examined the association of air pollution and odds of cardiac arrhythmia in older adults.

METHODS

Thirty two non-smoking older adults were evaluated on a weekly basis for 24 weeks during the summer and autumn of 2000 with a standardised 30 minute protocol that included continuous electrocardiogram measurements. A central ambient monitoring station provided daily concentrations of fine particles (PM(2.5), sulfate, elemental carbon) and gases. Sulfate was used as a marker of regional pollution. The authors used logistic mixed effects regression to examine the odds of having any supraventricular ectopy (SVE) or ventricular ectopy (VE) in association with increases in air pollution for moving average pollutant concentrations up to 10 days before the health assessment.

RESULTS

Participant specific mean counts of arrhythmia over the protocol varied between 0.1-363 for SVE and 0-350 for VE. The authors observed odds ratios for having SVE over the length of the protocol of 1.42 (95% CI 0.99 to 2.04), 1.70 (95% CI 1.12 to 2.57), and 1.78 (95% CI 0.95 to 3.35) for 10.0 microg/m3, 4.2 microg/m3, and 14.9 ppb increases in five day moving average PM2.5, sulfate, and ozone concentrations respectively. The other pollutants, including elemental carbon, showed no effect on arrhythmia. Participants reporting cardiovascular conditions (for example, previous myocardial infarction or hypertension) were the most susceptible to pollution induced SVE. The authors found no association of pollution with VE.

CONCLUSION

Increased levels of ambient sulfate and ozone may increase the risk of supraventricular arrhythmia in the elderly.

Traffic related pollution and heart rate variability in a panel of elderly subjects

BACKGROUND

Particulate air pollution has been associated with increased cardiovascular deaths and hospital admissions. To help understand the mechanisms, the types of particles most involved, and the types of persons most susceptible, the association between exposure to summertime air pollution and heart rate variability (HRV) was examined in a panel study of 28 elderly subjects.

METHODS

Subjects were seen once a week for up to 12 weeks and HRV (SDNN, r-MSSD, PNN50, low frequency/high frequency ratio (LFHFR)) was measured for approximately 30 minutes at each session using a defined protocol. Temperature, day of the week, and hour of the day were controlled, and dummy variables for each subject were controlled for subject specific risk factors.

RESULTS

PM2.5 was associated with r-MSSD (-10.1% change for an interquartile range (IQR) increase in exposure (95% CI -2.8 to -16.9)) and PNN50, but stronger associations were seen with black carbon, an indicator of traffic particles, which was also associated with SDNN (-4.6% per IQR (95% CI -2.0 to -7.2)) and LFHFR. Secondary particles were more weakly associated with r-MSSD, as was ozone. No associations were seen with SO2 or NO2. CO had similar patterns of association to black carbon, which disappeared after controlling for black carbon. Black carbon had a substantially higher effect on SDNN in subjects who had had a previous myocardial infarction (-12.7%, 95% CI -5.7 to -19.25).

CONCLUSIONS

Particles, especially from traffic, are associated with disturbances of autonomic control of the heart.

Predictors of indoor exposure to mouse allergen in urban and suburban homes in Boston

BACKGROUND

Mouse allergen exposure is prevalent among urban children with asthma. Little is known about mouse allergen exposure in children at risk for the development of allergic diseases.

AIMS OF THE STUDY

To assess indoor mouse allergen exposure in early life among children with parental history of asthma or allergies.

METHODS

Prospective birth cohort study of 498 children with a history of allergy or asthma in at least one parent living in metropolitan Boston.

RESULTS

Of the 498 participating children, 357 (71.7%) resided outside the city of Boston and 439 (90.7%) lived in households with incomes > 30,000 dollars. Mouse allergen was detected in 42% of the homes of study participants. In a multivariate analysis adjusting for sex, income, and endotoxin, black race [odds ratio (OR) = 3.0; 95% confidence interval (CI) = 1.3-6.6, P = 0.009], signs of mice in the home at age 2-3 months (OR = 3.0; 95% CI = 1.6-5.6, P = 0.0006), and kitchen cockroach allergen levels > or = 0.05 to < 2 U/g (OR = 1.8; 95% CI = 1.1-3.2, P = 0.02) were associated with detectable mouse allergen in the kitchen. In this model, living in a single detached house was inversely associated with detectable kitchen mouse allergen levels (OR = 0.4; 95% CI = 0.2-0.6, P = 0.0001).

CONCLUSION

Infants with a parental history of asthma or allergies are commonly exposed to mouse allergen in their homes. Among infants at high risk for atopy, predictors of increased mouse allergen levels included black race, reported mice exposure, and moderate levels of cockroach allergen.

Association between air pollution exposure and exhaled nitric oxide in an elderly population

BACKGROUND

Animal models suggest that the cardiovascular effects of air pollution result in part from inflammation caused by proinflammatory mediators originating in the lung. In a human study of the cardiovascular effects of air pollution, we aimed to evaluate the potential association between air pollution levels and the fraction of exhaled nitric oxide (FE(NO)), a non-invasive measure of airway inflammation.

METHODS

Breath samples were collected weekly between September and December 2000 in a community based group of elderly subjects (median age 70.7 years) in Steubenville, Ohio. The samples were analysed for NO. Air pollution levels were measured concurrently at a central site monitor.

RESULTS

An increase in the 24 hour average PM(2.5) concentration of 17.7 micro g/m(3) was associated with an increase in FE(NO) of 1.45 ppb (95% CI 0.33 to 2.57) in models adjusted for subject, week of study, day of the week, hour of the day, ambient barometric pressure, temperature, and relative humidity. This represents a change of approximately 15% compared with the mean FE(NO) in the cohort (9.9 ppb). A significant association was also observed for a 24 hour moving average of ambient NO (0.83 ppb increase, 95% CI 0.26 to 1.40). In two-pollutant models, the magnitude and precision of the PM(2.5) effect was not reduced and the ambient NO effect was no longer significant. The associations between FE(NO) and PM(2.5) were significantly higher in subjects with a doctor's diagnosis of COPD (p value for interaction = 0.03).

CONCLUSIONS

Ambient pollution may lead to airway inflammation as measured by FE(NO). These subclinical inflammatory changes may be an important step in the pathogenesis of the cardiopulmonary effects induced by exposure to air pollution.

Dustborne and airborne fungal propagules represent a different spectrum of fungi with differing relations to home characteristics

BACKGROUND

Exposure to fungi is often assessed by culturing floor dust or air samples. Our objective was to evaluate the relationships between dustborne and airborne fungi and to identify factors that modify these relationships.

METHODS

From November 1994 to September 1996 sequential duplicate 45-l air samples were collected in bedrooms of 496 homes in the Boston area, using a Burkard culture plate sampler. After air sampling, bedroom floors were sampled with a vacuum cleaner that was modified to collect dust in a cellulose extraction thimble. Dust was sieved, and the fine dust was dilution-plated onto DG-18 media.

RESULTS

Concentrations of total culturable fungi per gram of bedroom-floor dust were correlated weakly, but significantly, with those of indoor air (r = 0.13, P < 0.05). Concentrations of some individual taxa in the dust and indoor air were also weakly associated. Adjusting for the concentrations of fungi in outdoor air, dustborne fungal concentrations were positively associated with those in indoor air for the taxa Cladosporium and Penicillium, but not for total fungi. The indoor air fungal levels were often predicted by different covariates to those predicting fungal levels in dust. The type of housing (house or apartment) and the presence of carpeting were often predictive factors for dust fungi. In contrast, outdoor fungal levels were often predictive of the indoor air fungal levels.

CONCLUSIONS

Because our data do not indicate a strong overall relationship between culturable fungi in dust and indoor air, the results from these two methods (dust and air sampling) likely represent different types of potential fungal exposures to residents. It may be essential to collect both air and dust samples, as well as information on housing characteristics, as indicators for fungal exposure.

Treatment of mitochondrial cytopathies

Mitochondrial cytopathies are clinically and biochemically heterogeneous disorders affecting energy production. Because of the diverse symptoms spanning organ systems, the large number of biochemical and genetic defects, and an unpredictable clinical course, there are limited data regarding proven effective therapies. In general, treatments for mitochondrial cytopathies are intended to augment energy production as well as reduce the production of free radicals and other toxic metabolites that further limit the generation of cellular energy. Theoretically, treatment can be aimed at increasing respiratory chain activity by supplementing relative deficiencies of cofactors required for proper functioning. Possible strategies to consider may include dietary management, supplemental vitamins and cofactors, and/or specific medications aimed at a particular symptom.

Predictors of airborne endotoxin in the home

We identified home characteristics associated with the level of airborne endotoxin in 111 Boston-area homes enrolled in a cohort study of home exposures and childhood asthma, and we developed a predictive model to estimate airborne endotoxin. We measured endotoxin in family-room air and in dust from the baby's bed, family room, bedroom, and kitchen floor. Level of airborne endotoxin was weakly correlated (r < 0.3) with level of endotoxin in each of the four types of dust samples and was significantly correlated with endotoxin in family-room dust (p < 0.05). Endotoxin in family-room dust accounted for < 6% of the variability of airborne endotoxin. In a multivariate model, certain home characteristics were positively (p < 0.05) associated with airborne endotoxin. These included current presence of dog (difference in level, dog vs. no dog = 72%, partial R(2 )= 12.8%), past presence of dog (partial R(2) = 5.5%), and endotoxin level in family-room dust (partial R(2) = 5.3%). Use of a dehumidifier (partial R(2) = 6.4%) was negatively associated (p = 0.02; difference = -31%) with airborne endotoxin. Other home characteristics were identified as important determinants of increased airborne endotoxin in this model, but individual coefficients were not statistically significant (alpha = 0.05): total amount of fine dust collected in the home (partial R(2 )= 3.8%), concrete floor in family room (3.7%), water damage (3.6%), and use of cool-mist humidifier in past year (2.7%). This multivariate model explained 42% of the variability of airborne endotoxin levels, a substantial improvement over that with dust endotoxin alone. Airborne endotoxin in Boston-area homes appears to be determined by the presence of dogs, moisture sources, and increased amounts of settled dust.

Acute exposure to environmental tobacco smoke and heart rate variability

Environmental tobacco smoke (ETS) has been associated with cardiovascular mortality. Pathophysiologic pathways leading from ETS exposure to cardiopulmonary disease are still being explored. Reduced cardiac autonomic function, as measured by heart rate variability (HRV), has been associated with cardiac vulnerability and may represent an important pathophysiologic mechanism linking ETS and risk of cardiac mortality. In this study we evaluated acute ETS exposure in a commercial airport with changes in HRV in 16 adult nonsmokers. We conducted ambulatory electrocardiographic (ECG) monitoring for 8-hr periods while participants alternated 2 hr in nonsmoking and smoking areas. Nicotine and respirable suspended particle concentrations and participants' blood oxygen saturation were also monitored. We calculated time and frequency domain measures of HRV for periods in and out of the smoking area, and we evaluated associations with ETS using comparative statistics and regression modeling. ETS exposure was negatively associated with all measures of HRV. During exposure periods, we observed an average decrement of approximately 12% in the standard deviation of all normal-to-normal heart beat intervals (an estimate of overall HRV). ETS exposures were not associated with mean heart rate or blood oxygen saturation. Altered cardiac autonomic function, assessed by decrements in HRV, is associated with acute exposure to ETS and may be part of the pathophysiologic mechanisms linking ETS exposure and increased cardiac vulnerability.

Mitochondrial cytopathy in adults: what we know so far

Mitochondrial cytopathies are a diverse group of inherited and acquired disorders that result in inadequate energy production. They can be caused by inheritable genetic mutations, acquired somatic mutations, exposure to toxins (including some prescription medications), and the aging process itself. In addition, a number of well-described diseases can decrease mitochondrial energy production; these include hyperthyroidism, hypothyroidism, and hyperlipidemia.

Association of specific allergen sensitization with socioeconomic factors and allergic disease in a population of Boston women

BACKGROUND

Socioeconomic differences in allergic disease prevalence have been reported; asthma has been associated with poverty in the United States and hay fever and eczema with relative affluence elsewhere. It is not yet established to what degree such differences in disease prevalence reflect patterns of sensitization and specific allergen sensitivities.

OBJECTIVE

We analyzed specific and total IgE measurements in a sample of 458 women, enriched for allergic disease, from the metropolitan Boston area to establish the relation of allergen sensitization to markers of socioeconomic status (SES) and to the prevalence and socioeconomic pattern of allergic disease in this community.

METHODS

Total and specific IgE antibodies were measured with the UNICAP System; self-reported allergic disease, household income, education, and race-ethnicity were ascertained with a questionnaire; and a further marker of poverty (percentage living below the poverty level) in the women's area of residence was established on the basis of zip codes. Analysis was performed with SAS statistical software.

RESULTS

Markers of low SES were univariately associated with increases in total IgE, number of allergen sensitizations, and levels of specific IgE. Socioeconomic differences in sensitization to cockroach (35% vs 6% in the highest and lowest poverty areas), animal (44% vs 26%), and ragweed (49% vs 23%) allergens were most marked. Sensitization primarily to indoor inhalant allergens (not ragweed or ryegrass) were associated with an increased risk of asthma, even after adjustment for SES.

CONCLUSION

We have demonstrated a socioeconomic gradient in sensitization that concords with increased rates of asthma in less affluent communities in this population.

House dust endotoxin and wheeze in the first year of life

We examined endotoxin exposure and wheezing episodes during the first year of life in a birth cohort of 499 infants with one or both parents having a history of asthma or allergy. We measured endotoxin in settled dust from the baby's bed, bedroom floor, family room, and kitchen floor within the first 3 mo after birth. The primary outcomes were any wheeze (versus no wheeze), and repeated wheeze (versus one or no report of wheeze). We found a significant univariate association of elevated endotoxin (> or = 100 EU/ mg) in family room dust with increased risk of any wheeze (Relative Risk = 1.29, 95% CI = 1.03-1.62). The association was not confounded by cockroach allergen, lower respiratory illness (croup, bronchitis, bronchiolitis, and pneumonia), smoking during pregnancy, lower birth weight, maternal asthma, presence of dog, and race/ethnicity in a multivariate model; the multivariate relative risk (RR = 1.33) was marginally significant (95% CI: 1.00-1.76, p < 0.05). In a multivariate model, controlling for the above covariates, elevated endotoxin in family room dust was significantly associated with increased risk (RR = 1.56, 95% CI = 1.03-2.38) of repeated wheeze. These results suggest that home endotoxin exposure may independently increase risk of any wheeze and repeated wheeze during the first year of life for children with a familial predisposition to asthma or allergy.

Exposure to cockroach allergen in the home is associated with incident doctor-diagnosed asthma and recurrent wheezing

BACKGROUND

Indoor inhaled allergens have been repeatedly demonstrated to worsen asthma in sensitized individuals, but their role in incident asthma is more controversial.

OBJECTIVE

We investigated the relationship between exposure to allergens (dust mite, cat, and cockroach) measured in the home and incident doctor-diagnosed asthma and recurrent wheezing in children born to parents with asthma, allergies, or both.

METHODS

From an ongoing longitudinal family and birth cohort study, we identified 222 siblings (median age, 2.87 years) of the index children. Allergen levels in the home were measured from dust samples obtained at the beginning of the study. Incident doctor-diagnosed asthma and recurrent wheezing were determined from questionnaires administered at 14 months and 22 months after the initial questionnaire.

RESULTS

Thirteen (5.9%) children were reported to have incident asthma, twenty (9.0%) children had recurrent asthmatic wheezing, and 18 (8.1%) had recurrent wheezing without asthma. Compared with children living in homes with Bla g 1 or 2 levels of less than 0.05 U/g, children exposed to Bla g 1 or 2 levels of 0.05 to less than 2 U/g had a relative risk for incident asthma of 8.27 (95% confidence interval, 1.04-66.04), whereas children exposed to Bla g 1 or 2 levels of 2 U/g or greater had a relative risk for incident asthma of 35.87 (95% confidence interval, 4.49-286.62). Cockroach allergen exposure was likewise a significant predictor for recurrent asthmatic wheezing. Neither dust mite nor cat allergen levels were significantly associated with either outcome. These findings remained after control for several covariates.

CONCLUSION

Exposure to cockroach allergen early in life may contribute to the development of asthma in susceptible children.

Longitudinal study of dust and airborne endotoxin in the home

To characterize the seasonal variability of endotoxin levels, we measured endotoxin in dust from the bed, bedroom floor, and kitchen floor in 20 homes, and in air from the bedroom in 15 of the homes. All homes were located in the greater Boston, Massachusetts, area and were sampled each month from April 1995 to June 1996. Outdoor air was collected at two locations. We found greater within-home than between-home variance for bedroom floor, kitchen floor, and airborne endotoxin. However, the reverse was true for bed dust endotoxin. Thus, studies using single measurements of dust endotoxin are most likely to reliably distinguish between homes if bed dust is sampled. Dust endotoxin levels were not significantly associated with airborne endotoxin. Airborne endotoxin was significantly (p = 0. 04) and positively associated with absolute humidity in a mixed-effect model adjusting for a random home effect and fixed effect of sampling month and home characteristics. This finding implies that indoor humidity may be an important factor controlling endotoxin exposure. We found a significant (p < 0.05) seasonal effect in kitchen floor dust (spring > fall) and bedroom airborne endotoxin (spring > winter), but not in the other indoor samples. We found significant seasonal pattern in outdoor airborne endotoxin (summer > winter).

Environmental tobacco smoke, indoor allergens, and childhood asthma

Both environmental tobacco smoke and indoor allergens can exacerbate already established childhood albeit primarily through quite disparate mechanisms. In infancy and childhood, environmental tobacco smoke (ETS) exposure is associated with measures of decreased flow in the airways, bronchial hyperresponsiveness, and increased respiratory infections, but the relationship between ETS and allergy is poorly understood. Indoor allergens from dust mite, cockroach, and cat can be associated with asthma exacerbation in children sensitized to the specific allergens. The precise role of either ETS or indoor allergens in the development of asthma is less well understood. The strong and consistent association between ETS and asthma development in young children may relate to both prenatal and postnatal influences on airway caliber or bronchial responsiveness. Dust mite allergen levels predict asthma in children sensitized to dust mite. The tendency to develop specific IgE antibodies to allergens (sensitization) is associated with and may be preceded by the development of a T-helper (Th)2 profile of cytokine release. The importance of either ETS or indoor allergens in the differentiation of T cells into a Th2-type profile of cytokine release or in the localization of immediate-type allergic responses to the lung is unknown. This article evaluates the strength of the evidence that ETS or indoor allergens influence asthma exacerbation and asthma development in children. We also selectively review data for the effectiveness of allergen reduction in reducing asthma symptoms and present a potential research agenda regarding these two broad areas of environmental exposure and their relationship to childhood asthma.

Children at risk for asthma: home allergen levels, lymphocyte proliferation, and wheeze

BACKGROUND

Allergic asthma is a common childhood disease. Although T-lymphocyte activation plays a critical role in allergic asthma, the environmental factors promoting lymphocyte activation in children are not well defined.

OBJECTIVE

In a cohort of children at risk for asthma (n = 114), we determined whether the levels of cockroach (Bla g 1 or 2), house dust mite (Der f 1), and cat allergen (Fel d 1) in the home during infancy was associated with subsequent allergen-specific lymphocyte proliferation in later life.

METHODS

Dust samples from multiple sites in the home were collected at 3 months of age and were measured for allergen levels. Serial questionnaires were applied. At a median age of 2 years, PBMCs were isolated and lymphocyte proliferation to the home allergens and PHA was determined.

RESULTS

Increased lymphocyte proliferative responses to Bla g 2 were associated with higher home levels of Bla g 1 or 2 (P for trend with kitchen Bla g levels =.011), in analyses adjusting for cold in the past week. Proliferative responses to Der f 1 were higher in homes with family room levels of Der f 1 > or =10 microg/g dust than in homes with Der f 1 <2 microg/g, but differences were not significant in analyses adjusting for cold (P =. 15). Repeated wheeze in the first 2 years of life was associated with increased allergen-specific and PHA proliferative responses.

CONCLUSION

Early-life cockroach allergen exposure at 3 months of age predicts allergen-specific lymphocyte proliferative responses at a median of 2 years of age.

Socioeconomic predictors of high allergen levels in homes in the greater Boston area

In the United States, childhood asthma morbidity and prevalence rates are the highest in less affluent urban minority communities. More than 80% of childhood asthmatics are allergic to one or more inhalant allergens. We evaluated whether socioeconomic status was associated with a differential in the levels and types of indoor home allergens. Dust samples for an ELISA allergen assay were collected from the homes of 499 families as part of a metropolitan Boston, Massachusetts, longitudinal birth cohort study of home allergens and asthma in children with a parental history of asthma or allergy. The proportion of homes with maximum home allergen levels in the highest category was 42% for dust mite allergen (> or = 10 microg/g Der p 1 or Der f 1), 13% for cockroach allergen (> or = 2 U/g Bla g 1 or Bla g 2), 26% for cat allergen (> or = 8 microg/g Fel d 1), and 20% for dog allergen (> or = 10 microg/g Can f 1). Homes in the high-poverty area (> 20% of the population below the poverty level) were more likely to have high cockroach allergen levels than homes in the low-poverty area [51 vs. 3%; OR, 33; 95% confidence interval (CI), 12-90], but less likely to have high levels of dust mite allergen (16 vs. 53%; OR, 0.2; CI, 0.1-0.4). Lower family income, less maternal education, and race/ethnicity (black or Hispanic vs. white) were also associated with a lower risk of high dust mite levels and a greater risk of high cockroach allergen levels. Within a single U.S. metropolitan area we found marked between-community differences in the types of allergens present in the home, but not necessarily in the overall burden of allergen exposure.

Ambient pollution and heart rate variability

BACKGROUND

We investigated associations between ambient pollution levels and cardiovascular function in a repeated measures study including 163 observations on twenty-one 53- to 87-year-old active Boston residents observed up to 12 times from June to September 1997. Particles with aerodynamic diameter </=2.5 microm (PM(2.5)) were measured continuously using a tapered element oscillating microbalance.

METHODS AND RESULTS

The protocol involved 25 minutes per week of continuous Holter ECG monitoring, including 5 minutes of rest, 5 minutes of standing, 5 minutes of exercise outdoors, 5 minutes of recovery, and 20 cycles of slow breathing. Heart rate variability (HRV) was assessed through time domain variables: the standard deviation of normal RR intervals (SDNN) and the square root of the mean of the squared differences between adjacent normal RR intervals (r-MSSD). Mean 4-hour PM(2.5) levels ranged from 3 to 49 microg/m(3); 1-hour ozone levels ranged from 1 to 77 ppb. In multivariate analyses, significantly less HRV (SDNN and r-MSSD) was associated with elevated PM(2.5). During slow breathing, a reduction in r-MSSD of 6.1 ms was associated with an interquartile (14.3 microg/m(3)) increase in PM(2.5) during the hour of and the 3 hours previous to the Holter session (P=0.006). During slow breathing, a multiple pollution model was associated with a reduction in r-MSSD of 5.4 ms (P=0.02) and 5.5 ms (P=0.03) for interquartile changes in PM(2.5) and ozone, respectively, resulting in a combined effect equivalent to a 33% reduction in the mean r-MSSD.

CONCLUSIONS

Particle and ozone exposure may decrease vagal tone, resulting in reduced HRV.

Air pollution and incidence of cardiac arrhythmia

Air pollution episodes have been associated with increased cardiovascular hospital admissions and mortality in time-series studies. We tested the hypothesis that patients with implanted cardioverter defibrillators experience potentially life-threatening arrhythmias after such air pollution episodes. We compared defibrillator discharge interventions among 100 patients with such devices in eastern Massachusetts, according to variations in concentrations of particulate matter, black carbon, and gaseous air pollutants that were measured daily for the years 1995 through 1997. A 26-ppb increase in nitrogen dioxide was associated with increased defibrillator interventions 2 days later (odds ratio = 1.8; 95% confidence interval = 1.1-2.9). Patients with ten or more interventions experienced increased arrhythmias in association with nitrogen dioxide, carbon monoxide, black carbon, and fine particle mass. These results suggest that elevated levels air pollutants are associated with potentially life-threatening arrhythmia leading to therapeutic interventions by an implanted cardioverter defibrillator.

Race, socioeconomic factors, and area of residence are associated with asthma prevalence

Asthma prevalence in the United States has been reported to be higher in minority groups such as Blacks and Hispanics. Because a disproportionate number of individuals from such minority groups are of low socioeconomic status (SES), it is unclear how much of the racial/ethnic differences in asthma prevalence is related to low SES. We investigated the effect of SES on the relationship between race/ethnicity and asthma prevalence in a cohort of families with a history of asthma or allergies from the Boston, Massachusetts area. From 499 families, a cohort of 998 parents and 307 children was identified. We used total yearly family income (<$50,000 vs. > or = $50, 000), highest level of education (< or = high school vs. > or = college), and residence in high-poverty areas vs. low-poverty areas as measures of SES. Yearly family income <$50,000, < or = high school education, and residence in high poverty areas were all associated with increased risks for asthma in both cohorts. In the parental cohort, Blacks and Hispanics (OR = 2.1, 95% CI = 1.5, 2.8; and OR = 2.2, 95% CI = 1.5, 3.2, respectively) were at greater risk for asthma than Whites. In the cohort of children, Black and Hispanic children (OR = 2.9, 95% CI = 1.0, 8.0; and OR = 5.3, 95% CI = 1.6, 17.5, respectively) were also at increased risk for asthma. When the three measures of SES were included in the multivariable models, the risks associated with Blacks and Hispanics decreased in both cohorts: OR = 1.4, 95% CI = 0.9, 2.0; and OR = 1.6, 95% CI = 1.0, 2. 6, respectively, for the parents; and OR = 0.8, 95% CI = 0.2, 3.0; and 2.5, 95% CI = 0.5, 11.7, respectively, for the children. We conclude that a large proportion of the racial/ethnic differences in asthma prevalence in our study is explained by factors related to income, area of residence, and level of education.

Heart rate variability associated with particulate air pollution

BACKGROUND

Epidemiologic studies have linked fine particulate air pollution with cardiopulmonary mortality, yet underlying biologic mechanisms remain unknown. Changes in heart rate variability (HRV) may reflect changes in cardiac autonomic function and risk of sudden cardiac death. This study evaluated changes in mean heart rate and HRV in human beings associated with changes in exposure to particulate air pollution.

METHODS

Repeated ambulatory electrocardiographic monitoring was conducted on 7 subjects for a total of 29 person-days before, during, and after episodes of elevated pollution. Mean HR, the standard deviation of normal-to-normal (NN) intervals (SDNN), the standard deviation of the averages of NN intervals in all 5-minute segments of the recording (SDANN), and the square root of the mean of squared differences between adjacent NN intervals (r-MSSD) were calculated for 24-hour and 6-hour time segments. Associations of HRV with particulate pollution levels were evaluated with fixed-effects regression models.

RESULTS

After controlling for differences across patients, elevated particulate levels were associated with (1) increased mean HR, (2) decreased SDNN, a measure of overall HRV, (3) decreased SDANN, a measure that corresponds to ultralow frequency variability, and (4) increased r-MSSD, a measure that corresponds to high-frequency variability. The associations between HRV and particulates were small but persisted even after controlling for mean HR.

CONCLUSIONS

This study suggests that changes in cardiac autonomic function reflected by changes in mean HR and HRV may be part of the pathophysiologic mechanisms or pathways linking cardiovascular mortality and particulate air pollution.

Monthly measurements of indoor allergens and the influence of housing type in a northeastern US city

BACKGROUND

We examined seasonal variation of dust-mite (Der f 1 and Der p 1), cat (Fel d 1), and cockroach (Bla g 1) allergens in Boston, while adjusting for other covariates. Limited data are available on seasonal patterns of indoor allergen concentrations for different geographic regions in the USA. Understanding within-home seasonal variation of allergens is important epidemiologically and clinically.

METHODS

From June 1995 to June 1996, dust samples were vacuumed monthly from the bed, bedroom floor, and kitchen of 20 homes. Indoor temperatures were measured monthly and used in calculating relative and absolute humidity. Monthly home characteristics questionnaires were completed by an adult resident of each home. Dust samples were assayed by enzyme-linked immunosorbent assays.

RESULTS

Der f 1 and Der p 1 in beds and floors peaked in the autumn months, Fel d 1 peaked in winter and spring, and Bla g 1 was highest in summer. Dust-mite allergen concentrations were 1.9-2.4 times higher in autumn than spring, but the levels in beds were 19-31 times higher in houses than those in apartments. Although Fel d 1 levels in beds were 2.4 times higher in spring than summer, homes with cats had levels 224 times higher than those without cats. Similarly, Bla g 1 levels in kitchens were 2.1 times higher in summer than winter, but apartments had levels five times higher than those of houses.

CONCLUSIONS

Sampling season is a source of within-home dust-mite, cat, and cockroach allergen variation in the northeastern USA. However, the influence of housing type and owning a cat far outweighed the seasonal variation of these indoor allergens.

Day care attendance in the first year of life and illnesses of the upper and lower respiratory tract in children with a familial history of atopy

OBJECTIVE

To examine the relationship between day care attendance and illnesses of the upper and lower respiratory tract in the first year of life.

STUDY DESIGN

Prospective birth cohort study.

METHODS

Children (N = 498) who had at least 1 parent with a history of allergy or asthma were enrolled at birth and followed prospectively for the first year of life. A home visit at 2 to 3 months of age and bimonthly telephone questionnaires were used to obtain information on day care arrangements, home characteristics, respiratory symptoms, and physician-diagnosed illnesses of the upper and lower respiratory tract.

RESULTS

Day care attendance in the first year of life was associated with two or more doctor-diagnosed ear infections (OR: 2.4; 95% CI: 1.7-3.6), three or more parental reports of runny or stuffed nose (OR: 3.2; 95% CI: 1.9-5.5), a doctor's diagnosis of sinusitis (OR: 2.2; 95% CI: 1.1-4.2), and doctor-diagnosed lower respiratory illnesses (croup, bronchitis, bronchiolitis, and pneumonia; OR: 1.6; 95% CI: 1.0-2.4). For children attending day care, exposure to pets in day care, the presence of a rug or carpet in the area where the child slept in day care, and a nonresidential setting for day care all were independent predictors of two or more doctor-diagnosed ear infections.

CONCLUSIONS

The results suggest that day care increases the risk of illnesses of the upper and lower respiratory tract in the first year of life for children with a familial history of atopy. Specific environmental exposures within day care, such as the presence of pets or having a rug or carpet in the area where children sleep, may increase the risk of recurrent ear infections in the first year of life among children with familial history of atopy who attend day care.

Treatment strategies for medulloblastoma and primitive neuroectodermal tumors

Medulloblastoma and primitive neuroectodermal tumors (PNETs) are the most common malignant brain tumors in children. The concern for late sequelae of neuraxis irradiation and the obligation to improve disease-free survival in children who harbor malignant brain tumors has led to the additional provision of systemic chemotherapy to standard- and reduced-dose radiotherapy, as well as to the evaluation of alternate modes of radiotherapy delivery. Analysis of evidence has suggested that chemotherapy has an impact on length of survival in children with medulloblastoma and PNETs. The question remains as to whether chemotherapy combined with reduced-dose radiotherapy provides greater benefit than standard-dose radiotherapy alone, and which subset of children the treatment most benefits. Also unanswered is the question of whether chemotherapy can serve as the primary treatment in infants with these lesions. In an attempt to help answer these questions, the authors review the major chemotherapy and radiotherapy trials for newly diagnosed patients and those with recurrent medulloblastoma and PNETs.

Predictors of repeated wheeze in the first year of life: the relative roles of cockroach, birth weight, acute lower respiratory illness, and maternal smoking

While more than 80% of childhood asthmatics are allergic to one or more inhaled allergens, the role of inhaled allergens in the induction of wheeze in the first year of life is unknown. In a prospective birth-cohort study of 499 children of asthmatic/allergic parents from metropolitan Boston, we examined home allergen concentrations measured within the first 3 mo of life as predictors of repeated wheeze episodes in the first year of life. In multivariate analyses adjusting for maternal asthma and dog in the home, predictors of two or more wheeze episodes in the first year of life included maternal smoking during pregnancy (relative risk [RR] = 1.83; 95% confidence limit [CL]: 1.12, 3.00), lower respiratory illness in the first year of life (croup, bronchitis, bronchiolitis, or pneumonia) (RR = 2.25; 95% CL:1.58, 3.19), low birthweight (RR = 1.28, 95% confidence interval [CI]: 1.04, 1.58 for an interquartile difference), and Bla g 1 or 2 (cockroach) allergen level in the family room > 0.05 U/g dust (RR = 1.76; 95% CL: 1.20, 2.57). Cockroach allergen in the family room and repeated wheeze remained significant after adjustment for socioeconomic factors including race and income (RR = 1.63; 95% CL: 1.05, 2.55). It is unknown whether the association between cockroach and repeated wheeze in infancy represents a cockroach-related increased risk of bronchial inflammation through nonallergenic or allergenic mechanisms.

Air pollution and infant mortality in Mexico City

Historic air pollution episodes of the 1950s led to acute increases in infant mortality, and some recent epidemiologic studies suggest that infant or child mortality may still result from air pollution at current levels. To investigate the evidence for such an association, we conducted a time-series study of infant mortality in the southwestern part of Mexico City in the years 1993 to 1995 using mortality data from death registrations and air pollution measurements from a monitoring station we operated. Excess infant mortality was associated with the level of fine particles in the days before death, with the strongest association observed for the average concentration of fine particles during the period 3 to 5 days previously: a 10-microg m(-3) increase in the mean level of fine particles during these 3 days was associated with a 6.9% excess of infant deaths (95% confidence interval 2.5-11.3%). Infant mortality was also associated with the levels of nitrogen dioxide and ozone 3 to 5 days before death, but not as consistently as with particles.

Cockroach allergy and asthma in a 30-year-old man

A growing body of evidence has implicated allergens derived from cockroaches as an important environmental factor that may aggravate asthma in sensitized persons. We present the case of a 30-year-old man with asthma and a cockroach allergy. Allergy skin testing confirmed hypersensitivity to cockroach extract, and a home visit revealed visual evidence of infestation and the presence of Bla g 1 German cockroach allergen in vacuumed dust. As is typical of patients with a cockroach allergy and asthma, multiple factors in addition to cockroach allergen appeared to aggravate the patient's asthma. A multimodality therapeutic regimen, which included medications as well as cleaning of the home, integrated pest management, and professional application of chemical controls, resulted in substantial clinical improvement. The pathophysiology, epidemiology, and clinical features of cockroach-allergic asthma are reviewed, and an approach to diagnosis and management is suggested.

Particulate and ozone pollutant effects on the respiratory function of children in southwest Mexico City

We assessed the contributions of particulate matter with aerodynamic diameters < or =10 and < or =2.5 microm (PM2.5 and PM10) and ozone (O3) to peak expiratory flow (PEF) and respiratory symptoms in 40 schoolchildren 8-11 years of age for 59 days during three periods in 1991 at a school in southwest Mexico City. We measured peak expiratory flow in the morning on the children's arrival at school and in the afternoon before their departure from school. Separately for morning and afternoon, we normalized each child's daily measurement of peak flow by subtracting his or her mean peak flow from the daily measurement. Child-specific deviations were averaged to obtain a morning and afternoon mean deviation (APEF) for each day. Mean 24-hour O3 level was 52 parts per billion (ppb; maximum 103 ppb); mean 24-hour PM2.5 and PM10 were 30 microg/m3 (maximum 69 microg/m3) and 49 microg/m3 (maximum 87 microg/m3), respectively. We adjusted moving average and polynomial distributed lag multiple regression analyses of APEF vs pollution for minimum daily temperature, trend, and season. We examined effects of PM2.5, PM10, and O3, on deltaPEF separately and in joint models. The models indicated a role for both particles and O3 in the reduction of peak expiratory flow, with shorter lags between exposure and reduction in peak expiratory flow for O3 than for particle exposure (0-4 vs 4-7 days). The joint effect of 7 days of exposure to the interquartile range of PM2.5 (17 microg/m3) and O3 (25 ppb) predicted a 7.1% (95% confidence interval = 11.0-3.9) reduction in morning peak expiratory flow. Pollutant exposure also predicted higher rates of phlegm; colinearity between pollutants limited the potential to distinguish the relative contribution of individual pollutants. In an area with chronically high ambient O3 levels, school children responded with reduced lung function to both O3 and particulate exposures within the previous 1 to 2 weeks.

Mortality and ambient fine particles in southwest Mexico City, 1993-1995

++Epidemiologic studies have focused attention on the health effects of fine particulate air pollutants <2.5 microm in diameter (PM2.5). To further characterize the potential effects of fine particles, we investigated the relationship of air pollution to mortality in Mexico City during 1993-1995. The concentration of PM2.5 was measured on a 24-hr integrated basis; concentrations of NO2 and ozone were measured hourly and reduced to 24-hr means. Daily mortality was determined from death registration records, and Poisson regression was used to model daily death counts as a function of air pollutant levels on the same and previous days, while controlling for temperature and periodic cycles. Without taking other air pollutants into account, a 10 microg/m3 increase in the level of PM2.5 was associated with a 1.4% increase in total mortality, both on the current day and 4 days after exposure [95% confidence interval (CI), 0.2-2.5]. An equivalent increase in PM2.5 was also associated with somewhat larger excesses of deaths among people over 65 years of age and from cardiovascular and respiratory causes, which occurred after a lag of 4 days. The mean concentration of ozone over a 2-day period was associated with a 1.8% increase in mortality from cardiovascular diseases. NO2 was not consistently related to mortality. Fine particles had an independent effect on mortality when modeled simultaneously with other pollutants, and the association of ozone with cardiovascular mortality was strengthened after adjusting for NO2 and PM2.5. These results support previous findings that urban air pollution at current levels leads to excess mortality and suggest that fine particles may play a causal role in producing that excess.

Mortality and ambient fine particles in southwest Mexico City, 1993-1995

++Epidemiologic studies have focused attention on the health effects of fine particulate air pollutants <2.5 microm in diameter (PM2.5). To further characterize the potential effects of fine particles, we investigated the relationship of air pollution to mortality in Mexico City during 1993-1995. The concentration of PM2.5 was measured on a 24-hr integrated basis; concentrations of NO2 and ozone were measured hourly and reduced to 24-hr means. Daily mortality was determined from death registration records, and Poisson regression was used to model daily death counts as a function of air pollutant levels on the same and previous days, while controlling for temperature and periodic cycles. Without taking other air pollutants into account, a 10 microg/m3 increase in the level of PM2.5 was associated with a 1.4% increase in total mortality, both on the current day and 4 days after exposure [95% confidence interval (CI), 0.2-2.5]. An equivalent increase in PM2.5 was also associated with somewhat larger excesses of deaths among people over 65 years of age and from cardiovascular and respiratory causes, which occurred after a lag of 4 days. The mean concentration of ozone over a 2-day period was associated with a 1.8% increase in mortality from cardiovascular diseases. NO2 was not consistently related to mortality. Fine particles had an independent effect on mortality when modeled simultaneously with other pollutants, and the association of ozone with cardiovascular mortality was strengthened after adjusting for NO2 and PM2.5. These results support previous findings that urban air pollution at current levels leads to excess mortality and suggest that fine particles may play a causal role in producing that excess.

Parental history and the risk for childhood asthma. Does mother confer more risk than father?

Although heredity plays a major role in asthma and in other allergic diseases, mechanisms underlying the inheritance of these disorders are poorly understood, as is the relative contribution of maternal and paternal conditions to risk of disease. We investigated doctor-diagnosed maternal and paternal asthma, eczema, and hay fever as cross-sectional predictors of childhood asthma and allergic disease in 306 children with a median age of 3.5 yr from families in which at least one parent had a history of either asthma or other allergic conditions. For both childhood asthma and eczema, the strongest parental predictors were the same conditions in the parents. For asthma in particular, maternal asthma was most strongly associated with asthma in the child over all ages in both univariate (OR = 3.2, 95% CI = 1.5 to 6.7) and multivariable (OR = 4.1, 95% CI = 1.7 to 10.1) models. Paternal asthma was weakly associated with childhood asthma in the univariate model (OR = 1.4, 95% CI = 0.6 to 3.2), but this association increased in magnitude in the multivariable model (OR = 2.7, 95% CI = 1.0 to 7.2). Among the children < 5 yr of age, the risk for childhood asthma associated with maternal asthma (OR = 5.0, 95% CI = 1.7 to 14.9) was greater than the risk associated with paternal asthma (OR = 1.6, 95% CI = 0. 5 to 5.9), whereas both maternal asthma and paternal asthma were associated with similar risks among children >= 5 yr of age (OR = 4. 6, 95% CI = 1.1 to 19.0 and OR = 4.1, 95% CI = 1.0 to 16.0, respectively). The odds of having a child with asthma were three times greater in families with one asthmatic parent and six times greater in families with two asthmatic parents than in families where only one parent had inhalant allergy without asthma; furthermore, inhalant allergy in one parent also conferred additional risk in the presence of asthma in the other parent. Further investigation is needed into the relative importance of genetic factors and in utero and postnatal exposures in determining the differential effects of maternal and paternal asthma on the development of childhood asthma.

Limitations of a home characteristics questionnaire as a predictor of indoor allergen levels

We examined associations between reported home characteristics and levels of indoor allergens in 499 homes of a birth cohort of children of allergic/asthmatic families from the Boston area. The risk of having dust mite allergen (Der f 1 or Der p 1) > or = 2 microg/g on the bedroom floor was highest in houses, but 16% of apartments had levels this high. Compared with that from smooth floors, dust from carpeted bedroom floors had 2.1 times the risk of dust mite allergen > or = 10 microg/g, but levels exceeded 2 microg/g in 32% of uncarpeted floors. The risk of dust mite allergen > or = 10 microg/g of dust from plastic-encased mattresses was 0.5 times that for cloth mattresses, but levels in 21% of plastic-encased mattresses were > or = 2 microg/g. In 93% of homes with and 3% of homes without cats, Fel d 1 was > or = 8 microg/g, but 34% of homes without cats had Fed d 1 > or = 1 microg/g. Cockroach allergen (Bla g 1 or Bla g 2) was > or = 2 U/g of kitchen dust in 26% of apartments and only 6% of houses, and it was detected in 48% of homes with no reported signs of cockroaches in the previous 12 mo. Home characteristics reporting is a relatively weak predictor of the absence of allergen, and exposure can occur even when no cats are present, beds are encased in plastic, no carpets are present, and no signs of cockroaches have been reported.

Effects of ozone and other pollutants on the pulmonary function of adult hikers

This study evaluated the acute effects of ambient ozone (O3), fine particulate matter (PM2.5), and strong aerosol acidity on the pulmonary function of exercising adults. During the summers of 1991 and 1992, volunteers (18-64 years of age) were solicited from hikers on Mt. Washington, New Hampshire. Volunteer nonsmokers with complete covariates (n = 530) had pulmonary function measured before and after their hikes. We calculated each hiker's posthike percentage change in forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), the ratio of these two (FEV1/FVC), forced expiratory flow between 25 and 75% of FVC(FEF25-75%), and peak expiratory flow rate (PEFR). Average O3 exposures ranged from 21 to 74 ppb. After adjustment for age,sex, smoking status (former versus never), history of asthma or wheeze, hours hiked, ambient temperature, and other covariates, there was a 2.6% decline in FEV1 [95% confidence interval (CI), 0.4-4.7; p = 0.02] and a 2.2% decline in FVC (CI, 0.8-3.5; p =0.003) for each 50 ppb increment in mean O3. There were consistent associations of decrements in both FVC (0.4% decline; CI,0.2-0.6, p = 0.001) and PEFR (0.8% decline; CI, 0.01-1.6; p = 0.05) with PM2.5 and of decrements in PEFR (0.4% decline; CI, 0.1-0.7; p = 0.02) with strong aerosol acidity across the interquartile range of these exposures. Hikers with asthma or a history of wheeze (n = 40) had fourfold greater responsiveness to ozone than others. With prolonged outdoor exercise, low-level exposures to O3, PM2.5, and strong aerosol acidity were associated with significant effects on pulmonary function among adults. Hikers with a history of asthma or wheeze had significantly greater air pollution-related changes in pulmonary function.